Check valve question

[BigDave]

Sounds right. Is the low water level in the spa at the same as the water level in the pool?

[Rockman59]

The spa sits about 3 feet above the pool level....when the main pump is running water goes into the spa then over a small waterfall into the pool. When the main pump goes off at the end of the day the water level in the spa is level with the exit point at the waterfall......in the morning before the main pump comes on again the water has gone down about a foot in the spa. When the main pump comes on it takes a couple of minutes to get the spa water level back to where it flows into pool...and the cycle continues. No problems with the pump....gotta be the check valve.